I wanted to publish a little information because I've seen a lot of debates on whether there are any differences. Background: I have a 98 290 with a single 454 Bravo 3, while I specifically wanted this under-powered combination, any time something isn't on point, I notice. I recently replaced the transom assembly (which comes from merc with the accordion), and was struggling to get on plane. After hours of diagnostics and a full tune up, I finally decided to hone in on the fact that the exhaust note had changed. After reading many opinions, mostly claiming that it is preference and noise reduction, I decided I'd gamble with the $50 part and try swapping out my bellows. Findings: The tube style bellows was just the boost I needed to get over the hump and on plane; I also regained about 100 rpm at WOT. However, as one would expect, its a straight win win. When I had the accordion, the acceleration from around 2500 to 3600 rpms was much faster, but the power curve would fall off right after that and not allow me to hit the 3800 I need to plane. Hope this information helps anyone wondering about this in the future.